NAME
LaTeX::TOM - A module for parsing, analyzing, and manipulating LaTeX
documents.
SYNOPSIS
use LaTeX::TOM;
$parser = LaTeX::TOM->new;
$document = $parser->parseFile('mypaper.tex');
$latex = $document->toLaTeX;
$specialnodes = $document->getNodesByCondition(
'$node->getNodeType eq \'TEXT\' &&
$node->getNodeText =~ /magic string/'
);
$sections = $document->getNodesByCondition(
'$node->getNodeType eq \'COMMAND\' &&
$node->getCommandName =~ /section$/'
);
$indexme = $document->getIndexableText;
$document->print;
DESCRIPTION
This module provides a parser which parses and interprets (though not
fully) LaTeX documents and returns a tree-based representation of what
it finds. This tree is a "LaTeX::TOM::Tree". The tree contains
"LaTeX::TOM::Node" nodes.
This module should be especially useful to anyone who wants to do
processing of LaTeX documents that requires extraction of plain-text
information, or altering of the plain-text components (or alternatively,
the math-text components).
COMPONENTS
LaTeX::TOM::Parser
The parser recognizes 3 parameters upon creation. The parameters, in
order, are
parse error handling (= 0 || 1 || 2)
Determines what happens when a parse error is encountered. 0 results
in a warning. 1 results in a die. 2 results in silence. Note that
particular groupings in LaTeX (i.e. newcommands and the like)
contain invalid TeX or LaTeX, so you nearly always need this
parameter to be 0 or 2 to completely parse the document.
read inputs flag (= 0 || 1)
This flag determines whether a scan for "\input" and "\input-like"
commands is performed, and the resulting called files parsed and
added to the parent parse tree. 0 means no, 1 means do it. Note that
this will happen recursively if it is turned on. Also,
bibliographies (.bbl files) are detected and included.
apply mappings flag (= 0 || 1)
This flag determines whether (most) user-defined mappings are
applied. This means "\defs", "\newcommands", and "\newenvironments".
This is critical for properly analyzing the content of the document,
as this must be phrased in terms of the semantics of the original
TeX and LaTeX commands, not ad hoc user macros. So, for instance, do
not expect plain-text extraction to work properly with this option
off.
The parser returns a "LaTeX::TOM::Tree" ($document in the SYNOPSIS).
LaTeX::TOM::Node
Nodes may be of the following types:
TEXT
"TEXT" nodes can be thought of as representing the plain-text
portions of the LaTeX document. This includes math and anything else
that is not a recognized TeX or LaTeX command, or user-defined
command. In reality, "TEXT" nodes contain commands that this parser
does not yet recognize the semantics of.
COMMAND
A "COMMAND" node represents a TeX command. It always has child nodes
in a tree, though the tree might be empty if the command operates on
zero parameters. An example of a command is
\textbf{blah}
This would parse into a "COMMAND" node for "textbf", which would
have a subtree containing the "TEXT" node with text ``blah.''
ENVIRONMENT
Similarly, TeX environments parse into "ENVIRONMENT" nodes, which
have metadata about the environment, along with a subtree
representing what is contained in the environment. For example,
\begin{equation}
r = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
\end{equation}
Would parse into an "ENVIRONMENT" node of the class ``equation''
with a child tree containing the result of parsing ``r = \frac{-b
\pm \sqrt{b^2 - 4ac}}{2a}.''
GROUP
A "GROUP" is like an anonymous "COMMAND". Since you can put whatever
you want in curly-braces ("{}") in TeX in order to make semantically
isolated regions, this separation is preserved by the parser. A
"GROUP" is just the subtree of the parsed contents of plain
curly-braces.
It is important to note that currently only the first "GROUP" in a
series of "GROUP"s following a LaTeX command will actually be parsed
into a "COMMAND" node. The reason is that, for the initial purposes
of this module, it was not necessary to recognize additional
"GROUP"s as additional parameters to the "COMMAND". However, this is
something that this module really should do eventually. Currently if
you want all the parameters to a multi-parametered command, you'll
need to pick out all the following "GROUP" nodes yourself.
Eventually this will become something like a list which is stored in
the "COMMAND" node, much like XML::DOM's treatment of attributes.
These are, in a sense, apart from the rest of the document tree.
Then "GROUP" nodes will become much more rare.
COMMENT
A "COMMENT" node is very similar to a "TEXT" node, except it is
specifically for lines beginning with ``%'' (the TeX comment
delimeter) or the right-hand portion of a line that has ``%'' at
some internal point.
LaTeX::TOM::Trees
As mentioned before, the Tree is the return result of a parse.
The tree is nothing more than an arrayref of Nodes, some of which may
contain their own trees. This is useful knowledge at this point, since
the user isn't provided with a full suite of convenient
tree-modification methods. However, Trees do already have some very
convenient methods, described in the next section.
METHODS
LaTeX::TOM
new
Instantiate a new parser object.
In this section all of the methods for each of the components are listed
and described.
LaTeX::TOM::Parser
The methods for the parser (aside from the constructor, discussed above)
are :
parseFile (filename)
Read in the contents of *filename* and parse them, returning a
"LaTeX::TOM::Tree".
parse (string)
Parse the string *string* and return a "LaTeX::TOM::Tree".
LaTeX::TOM::Tree
This section contains methods for the Trees returned by the parser.
copy
Duplicate a tree into new memory.
print
A debug print of the structure of the tree.
plainText
Returns an arrayref which is a list of strings representing the text
of all "getNodePlainTextFlag = 1" "TEXT" nodes, in an inorder
traversal.
indexableText
A method like the above but which goes one step further; it cleans
all of the returned text and concatenates it into a single string
which one could consider having all of the standard information
retrieval value for the document, making it useful for indexing.
toLaTeX
Return a string representing the LaTeX encoded by the tree. This is
especially useful to get a normal document again, after modifying
nodes of the tree.
getTopLevelNodes
Return a list of "LaTeX::TOM::Nodes" at the top level of the Tree.
getAllNodes
Return an arrayref with all nodes of the tree. This "flattens" the
tree.
getCommandNodesByName (name)
Return an arrayref with all "COMMAND" nodes in the tree which have a
name matching *name*.
getEnvironmentsByName (name)
Return an arrayref with all "ENVIRONMENT" nodes in the tree which
have a class matching *name*.
getNodesByCondition (expression)
This is a catch-all search method which can be used to pull out
nodes that match pretty much any perl expression, without manually
having to traverse the tree. *expression* is a valid perl expression
which makes reference to the perl variable $node when testing
something about the currently scrutinized node of the tree. See the
SYNOPSIS for examples.
getFirstNode
Returns the first node of the tree. This is useful if you want to
walk the tree yourself, starting with the first node.
LaTeX::TOM::Node
This section contains the methods for nodes of the parsed Trees.
getNodeType
Returns the type, one of "TEXT", "COMMAND", "ENVIRONMENT", "GROUP",
or "COMMENT", as described above.
getNodeText
Applicable for "TEXT" or "COMMENT" nodes; this returns the document
text they contain. This is undef for other node types.
setNodeText
Set the node text, also for "TEXT" and "COMMENT" nodes.
getNodeStartingPosition
Get the starting character position in the document of this node.
For "TEXT" and "COMMENT" nodes, this will be where the text begins.
For "ENVIRONMENT", "COMMAND", or "GROUP" nodes, this will be the
position of the *last* character of the opening identifier.
getNodeEndingPosition
Same as above, but for last character. For "GROUP", "ENVIRONMENT",
or "COMMAND" nodes, this will be the *first* character of the
closing identifier.
getNodeOuterStartingPosition
Same as getNodeStartingPosition, but for "GROUP", "ENVIRONMENT", or
"COMMAND" nodes, this returns the *first* character of the opening
identifier.
getNodeOuterEndingPosition
Same as getNodeEndingPosition, but for "GROUP", "ENVIRONMENT", or
"COMMAND" nodes, this returns the *last* character of the closing
identifier.
getNodeMathFlag
This applies to any node type. It is 1 if the node sets, or is
contained within, a math mode region. 0 otherwise. "TEXT" nodes
which have this flag as 1 can be assumed to be the actual
mathematics contained in the document.
getNodePlainTextFlag
This applies only to "TEXT" nodes. It is 1 if the node is non-math
and is visible (in other words, will end up being a part of the
output document). One would only want to index "TEXT" nodes with
this property, for information retrieval purposes.
getEnvironmentClass
This applies only to "ENVIRONMENT" nodes. Returns what class of
environment the node represents (the "X" in "\begin{X}" and
"\end{X}").
getCommandName
This applies only to "COMMAND" nodes. Returns the name of the
command (the "X" in "\X{...}").
getChildTree
This applies only to "COMMAND", "ENVIRONMENT", and "GROUP" nodes: it
returns the "LaTeX::TOM::Tree" which is ``under'' the calling node.
getFirstChild
This applies only to "COMMAND", "ENVIRONMENT", and "GROUP" nodes: it
returns the first node from the first level of the child subtree.
getLastChild
Same as above, but for the last node of the first level.
getPreviousSibling
Return the prior node on the same level of the tree.
getNextSibling
Same as above, but for following node.
getParent
Get the parent node of this node in the tree.
getNextGroupNode
This is an interesting function, and kind of a hack because of the
way the parser makes the current tree. Basically it will give you
the next sibling that is a "GROUP" node, until it either hits the
end of the tree level, a "TEXT" node which doesn't match "/^\s*$/",
or a "COMMAND" node.
This is useful for finding all "GROUP"ed parameters after a
"COMMAND" node (see comments for "GROUP" in the "COMPONENTS" /
"LaTeX::TOM::Node" section). You can just have a while loop that
calls this method until it gets "undef", and you'll know you've
found all the parameters to a command.
Note: this may be bad, but "TEXT" Nodes matching "/^\s*\[[0-9]+\]$/"
(optional parameter groups) are treated as if they were 'blank'.
CAVEATS
Due to the lack of tree-modification methods, currently this module is
mostly useful for minor modifications to the parsed document, for
instance, altering the text of "TEXT" nodes but not deleting the nodes.
Of course, the user can still do this by breaking abstraction and
directly modifying the Tree.
Also note that the parsing is not complete. This module was not written
with the intention of being able to produce output documents the way
``latex'' does. The intent was instead to be able to analyze and modify
the document on a logical level with regards to the content; it doesn't
care about the document formatting and outputting side of TeX/LaTeX.
There is much work still to be done. See the TODO list in the TOM.pm
source.
BUGS
Probably plenty. However, this module has performed fairly well on a set
of ~1000 research publications from the Computing Research Repository,
so I deemed it ``good enough'' to use for purposes similar to mine.
Please let the authors know of parser errors if you discover any.
CREDITS
Thanks to (in order of appearance) who have contributed valuable
suggestions & patches:
Otakar Smrz
Moritz Lenz
James Bowlin
AUTHORS
Written by Aaron Krowne
Maintained by Steven Schubiger
WEB SITE
Please see http://br.endernet.org/~akrowne/elaine/latex_tom/ for this
module's home on the WWW.
LICENSE
This program is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.
See